1. Field of the Invention
This invention relates to a memory card, and more specifically, this invention relates to the memory card that is provided with a security function.
2. Description of the Related Art
Recently, for instance, it is remarkable that a memory card comprising a nonvolatile memory has got to be downsized and provided with large memory size; therefore it raises the expectations that the available fields of such memory card will be expanded
As well as the downsizing of the memory card makes the card available to set to many devices, due to the large memory size the card can be applied to the device having mass data to be stored. If the memory card comprises the common specification, a plurality of devices can use the memory card.
Additionally, diversified changes come out with the devices to which the memory card will be applicable. That is to say, one is that the control of each device becomes be in common by using the language, such as JAVA and the like; those languages independent of any hardware. And another is that the network connection makes it possible to carry out the remote control operation and the information sharing.
And now, one of the prior arts for protecting the writing into the memory card is disclosed in Japanese Laid-open Publication No. 2000-99676. The prior art disclosed teaches that the memory card is provided with a switch to set the prohibition of writing data into the memory card, and in response to a request (query) from a control device (host computer) a control unit provided with the memory card transmits a setting conditions of the switch to the control device.
The above-mentioned related art is arranged so that the control device can execute the prohibition processing of the data writing according to the setting conditions of the switch.
As mentioned above, it raises expectations that the available fields of the memory card will be expanded due to the downsizing with large memory size, however, the card requires the security in order to promote the application of the card in various fields. In particular, in order to use the memory card to store information to be handled with care, such as private information and information for the e-commerce, the memory card must be provided with the reliable security. When the user uses a device in order to access the memory card, the use is not always in good faith. Therefore the security must be ensured also in the memory card instead of assuring only the security by the cooperation between the device and the memory card.
However, the prior art disclosed in the above Japanese Laid-open Publication No. 2000-99676 is to prevent the data from being deleted inadvertently by a user, and the memory card itself is not provided with the security.
In other words, the memory card disclosed in Japanese Laid-open publication No. 2000-99676 only informs the control device, like the mobile phone, of the information that the switch is on or off. Accordingly, in case where the control device is controlled maliciously, it is possible to write data into the memory card regardless of the information of the switch-on or switch-off, or without confirming the switch-on or switch-off. In addition, since the switch does not function at all regarding the reading data stored in the memory card, the data can be read without difficulty. It is the same with the floppy disk (R) that is used heretofore generally.
And, for instance, the data stored in the memory card has seemed to be safe before now, except the memory card is stolen and the data therein is read by any ill-disposed person.
However, it is apt to adopt the language without appointing the platform in these days, so that it is possible to let the (control) device execute the malicious program adopting such language. Moreover, it is apt to use devices connecting each other with the network, so that the malicious program can be downloaded to the (control) device in one way or another, and executed by the device. And the malicious program thus executed reads the data from the memory card, and the read data can be transmitted through the network. As a practical matter, there are many reports that some computer viruses work the same operation. Particularly, in case of accessing the memory card via wireless communication like the contactless IC card, there is a possibility that the memory card is accessed by any third party while the user is not aware of it.
Under such conditions, in spite of that the user carries the memory card in his hand, there is a lot of possibility that the data stored in the memory card is read out or tampered while the user is not conscious of it.